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1
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Understanding Radiation Damage to Cells Using Microbeams

100%
Folkard M., Prise K., Shao C., Gilchrist S., Schettino G., Michette A., Vojnovic B.
Acta Physica Polonica A
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2006
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vol. 109
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issue 3
257-264
EN
Cellular micro-irradiation techniques provide unique experimental opportunities for understanding how ionizing radiation interacts with living cells and tissues. Using microbeams, it is possible to deliver precise doses of radiation to selected individual cells, or sub-cellular targets in vitro. This technique continues to be applied to the investigation of a number of phenomena currently of great interest to the radiobiological community. In particular, it is the study of so-called "non-targeted" effects (where cells are seen to respond indirectly to ionizing radiation) that are benefiting most from the use of microbeam approaches.
2
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The GSI Heavy Ion Microbeam: A Tool for the Investigation of Cellular Response to High LET Radiations

100%
Barberet P., Heiss M., Du G., Fischer B., Taucher-Scholz G.
Acta Physica Polonica A
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2006
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vol. 109
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issue 3
329-334
EN
Since the mid 1990's, an increasing number of charged particle microbeams have been designed to deliver a preset number of ions to individual living cells with the micron resolution. These tools provide a powerful technique to investigate the cellular response to low doses of radiations. During the last years, the single ion hit facility in operation on the GSI microbeam since 1987 has been upgraded for the irradiation of individual living cells in vitro. This setup presents two main peculiarities compared to the microbeams used up to now for cell irradiation. First, the beam's micrometric size is obtained by magnetic focusing and not by a simple collimation. This allows obtaining a smaller beam spot, a better defined linear energy transfer, and a high irradiation throughput. Then, the GSI microbeam is able to focus ions from carbon to uranium with energies between 1.4 MeV/u to 11.4 MeV/u. The range of accessible linear energy transfer is thus considerably extended compared to light ions microbeam in operation today. The design of the GSI microbeam is described, including the beam control, the online cell localisation, the cell dish designed specifically for microbeam irradiation, and the cell irradiation procedures. Experimental tests performed to check the global aiming accuracy as well as the first cellular irradiations are presented.
3
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Improved Light Extraction Efficiency by Photonic Crystal Arrays on Transparent Contact Layer Using Focused Ion Beams

80%
Wu G., Tsai B., Kung S., Wu C.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
140-143
EN
Nitride-based thin-film materials have become increasingly important for the high brightness light-emitting diode applications. The improvements in light extraction and lower power consumption are highly desired. Although the internal quantum efficiency of GaN-based LED has been relatively high, only a small fraction of light can be extracted. In this study, a new design of two-dimensional photonic crystal array has been prepared on the top transparent contact layer of indium-tin oxide film to improve the light extraction efficiency using focused ion beam. The acceleration voltage of the Ga dual-beam nanotechnology system SMI 3050 was 30 kV and the ion beam current was 100 pA. The cylindrical air holes had the diameter of 150 nm and depth of 100 nm. The micro photoluminescence analysis results showed that the light output intensity could be 1.5 times of that of the non-patterned control sample. In addition, the structural damage from the focused ion beam drilling of GaN step could be eliminated. The excellent I-V characteristics have been maintained, and the external light extraction efficiency would be still improved for the LED devices.
4
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Optical Investigation of Plasma Formation Process by Interaction of Intense Electron Beams with Metallic Targets

80%
An W., Engelko V., Mueller G., Weisenburger A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 6
1183-1185
EN
Electron beams with energies ≥ 100 keV offer attractive possibilities to modify metallic surfaces. Numerous experiments with the electron accelerators GESA I and II showed excellent results regarding the improvement of mechanical properties and the enhancement of the corrosion resistance of the treated materials. The next step leads to further technological adaptation of the process that especially was focused on the adaptation of the electron beam to the surface geometry. For the treatment of the outer surface of tubes the electron beam facility GESA IV with a radial converged electron beam was designed. In first experiments unexpected electrical short-circuiting after different time periods occurred. Two major reasons could be identified: excessive plasma formation at the cathode and target plasma formation. The latter can be controlled by vacuum conditions and surface cleaning of the target, the first by controlling the duration of plasma formation at the cathode.
5
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Ion Beam Surface Modification of GaN Films for High Efficient Light Emitting Diodes

80%
Wu G., Lin Y., Tu K.
Acta Physica Polonica A
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2013
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vol. 123
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issue 5
884-887
EN
Focused gallium (Ga) ion beam technology has been proposed to modify the surface of GaN thin films. Due to the significant advancement in nitride semiconductors, the solid-state light emitting diodes will gradually replace fluorescent lamps in the next decade. However, further improvements in light extraction and power efficiency are still highly desired. GaN is limited by its high refractive index, with low light escape cone angle at about 24.6°. The external quantum efficiency is low due to the unwanted reflection and absorption. As the patterning technology scales down to the nanometer level, photonic crystal lattice in the visible light wavelength range can be achieved. Therefore, we improved the external efficiency by the new design of hexagonal photonic crystal lattice with air hole arrays in the diameter of 150 nm and the depth of 120 nm. The Ga beam was accelerated at 30 kV and the ion current was 100 pA. The plane wave expansion method along with the finite difference time domain was useful to investigate the quantum confinement. The nanopatterning by the focused ion beam could save time and processing step. In addition, we have successfully prepared blue InGaN/GaN samples with hexagonal period of 200 nm. The device micro-photoluminescence results have demonstrated that the peak illumination intensity was improved by 30%.
6
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Materials Patterning and Characterisation at the Nanometre Scale Using Focused MeV Ion Beams: Present Achievements and Future Prospects

80%
Grime G.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
467-472
EN
A key phenomenon in the interaction of MeV ions and solids is that the energy transferred from the primary ions to the target electrons is high compared with atomic and molecular binding energies, but low compared with the ion energy. This means that there is a high probability of modifying the chemical properties of the material (for patterning) or of inducing the emission of electromagnetic radiation (for analysis), yet the path of particle is changed by a negligible amount, which means that focused beams remain sharp even after penetrating long depths into the material. Developments in focusing MeV ions in recent years have pushed the useable beam diameters into the sub-micrometre region, which means that nuclear microbeams are poised to make an impact in both direct write fabrication and micro-analysis at length scales of interest in nanotechnology or microbiology. This paper reviews the science and technology underlying the use of nuclear microbeams (ion solid interactions, focusing systems) and reports on the present status and trends of applications in sub-micron scale applications.
7
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Optical Pattern Fabrication in Amorphous Silicon Carbide with High-Energy Focused Ion Beams

80%
Tsvetkova T., Takahashi S., Sellin P., Gomez-Morilla I., Angelov O., Dimova-Malinovska D., Zuk J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
56-59
EN
Topographic and optical patterns have been fabricated in a-SiC films with a focused high-energy (1 MeV) H^{+} and He^{+} ion beam and examined with near-field techniques. The patterns have been characterized with atomic force microscopy and scanning near-field optical microscopy to reveal local topography and optical absorption changes as a result of the focused high-energy ion beam induced modification. Apart of a considerable thickness change (thinning tendency), which has been observed in the ion-irradiated areas, the near-field measurements confirm increases of optical absorption in these areas. Although the size of the fabricated optical patterns is in the micron-scale, the present development of the technique allows in principle writing optical patterns up to the nanoscale (several tens of nanometers). The observed values of the optical contrast modulation are sufficient to justify the efficiency of the method for optical data recording using high-energy focused ion beams.
8
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Ion Microscopy and Tomography

80%
Butz T., Lehmann D., Reinert T., Spemann D., Vogt J.
Acta Physica Polonica A
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2001
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vol. 100
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issue 5
603-613
EN
The use of light ions for microscopy and tomography is illustrated by a variety of recent applications in materials and life sciences at the Leipzig high-energy ion-nanoprobe LIPSION with a short comparison to other microscopic techniques. The versatility of ion techniques is exemplified by Rutherford backscattering spectrometry maps of thin films of solar cell materials, particle induced X-ray emission maps of manganese in ancient human bones, particle induced X-ray emission on single aerosol particles withμm size, and scanning transmission ion microscopy and tomography on pigs knee cartilage. Finally, the design of a single ion single living cell bombardment facility is sketched for studies of the cellular response and microdosimetry.
9
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Two-Dimensional Simulations of H¯ Ions Extraction

70%
Turek M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
254-258
EN
The 2D particle-in-cell method based model of a negative ion source is presented. The spatial distributions of electrostatic potential and plasma component densities are presented. Changes of negative ion distribution and potential as well as the extracted H¯ current with the plasma grid bias voltage are investigated. The presence of the potential well near the plasma grid surface that traps the negative ions is shown. Increase of the H¯ ions density inside the chamber with the negative bias voltage is demonstrated. Influence of the H¯ ion flux outgoing from the plasma grid on the extracted current was checked: increase by factor 2 is observed when the flux rises 4 times. Current-voltage characteristics of the ion source are presented, saturation of the curve is observed above 50 kV.
10
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Calculations of Ion Beam Emittance for Hot Cavity Ion Source

70%
Turek M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
931-934
EN
Emittance of short-lived nuclide beams produced in hot cavity ion sources is calculated. Influence of half-life period as well as the average sticking time on beam emittance is under investigation. Two different shapes of ionizer cavity are considered: almost fully spherical and hemispherical ones. Changes of beam emittance due to the extraction channel geometry (its diameter and length) are studied. A new concept of scaled efficiency (ion source brightness analogon) is introduced in order to compare the two-ion source configurations. Phase space portraits of the extracted beams are presented.
11
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Ion and Electron Beam Induced Luminescence οf Rare Earth Doped YAG Crystals

36%
Gawlik G., Sarnecki J., Jóźwik I., Jagielski J., Pawłowska M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
181-183
EN
The aim of this work was the evaluation of ion-beam induced luminescence for the characterization of luminescent oxide materials containing rare earth elements. The yttrium aluminium garnet epilayers doped with Nd, Pr, Ho, and Tm atoms were used. The ion-beam induced luminescence spectra were excited using 100 keV H_2^{+} ion beam and were recorded in the wavelengths ranging from 300 nm up to 1000 nm. The separate parts of the surface of the same samples were used for ion-beam induced luminescence and cathodoluminescence experiments. Cathodoluminescence spectra have been recorded in the range from 370 nm up to 850 nm at 20 keV e-beam in scanning electron microscope equipped with a grating spectrometer coupled with a photomultiplier. The observed narrow ion-beam induced luminescence lines can be ascribed to the well known radiative transitions in the rare-earth ions in the YAG crystals. The cathodoluminescence spectra reveal essentially the same emission lines as ion-beam induced luminescence. The decrease of the ion-beam induced luminescence lines intensity has been observed under the increasing ion fluences. The ion-beam induced luminescence may be used for characterization of transparent luminescent materials as an alternative method for cathodoluminescence and can be especially useful for observation of ion-beam damage formation in crystals.
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